Habitat

Greater grisons occupy a wide variety of terrestrial habitats, though they are generally found near streams, rivers or wetlands. Much of their time is spent in closed habitats including deciduous, rain, tropical or dry forest and shrub woodland. They have also been observed in open savanna, as well as cultivated areas such as plantations, cane fields or partially flooded rice fields. Galictis vittata occurs at elevations as high as 1,500 m above sea level, though it is usually found at lower elevations, most often below 500 m. (Kaufmann and Kaufmann, 1965; Leopold, 1972; Ramirez-Pulido, et al., 2005; Sunquist, et al., 1989; Timm, et al., 1989; Yensen and Tarifa, 2003a)

Physical Description

Greater grisons are often described as large weasels. They have long, slim bodies, with short legs and a short, long-haired tail. Their toes have pearlescent blue claws and are padded and partially webbed along approximately three quarters of their length. Galictis vittata has a small, flat head with small, whitish, relatively broad, rounded ears and brown or black eyes that reflect blue light in the dark. Most striking of all is the coloration of their fur, which itself is fairly coarse, with a softer undercoat. Their dorsum is grey and separated from their black or grizzled under-parts by a light-colored, half-inch wide stripe running across their forehead and down the sides of either shoulder. Greater grisons are similar in appearance to their close relative, lesser grisons, but can be distinguished from the latter based on their larger size and their white or grey-tipped dorsal guard hairs, compared to the buff yellow-tipped dorsal guard hairs of lesser grisons. Their body length, including their tail, ranges from 60 to 76 cm, with weight records ranging from 1.4 to 3.8 kg. Female greater grisons tend to be slightly smaller and more slender than males. One team of researchers recorded a length of 68.58 cm for their captive male grison, compared to 60.96 cm for their captive female. Similarly, the captive male had an average mass of 3.3 kg compared to 1.8 kg for the female, a difference of 1.5 kg. As is typical of most mustelid species, males have a baculum. Both males and females have anal glands on either side of their anus. The dental formula for this species is I3/3 + C1/1 + P3/3 + M1/2, giving Galictis vittata a total of 34 teeth. (Bisbal E., 1986; Dalquest and Roberts, 1951; Husson, 1978; Kaufmann and Kaufmann, 1965; Leopold, 1972; Mondolfi, 1987; Ramirez-Pulido, et al., 2005; Yensen and Tarifa, 2003a)

Reproduction

The birth of their offspring has been recorded in every month between March and October, excluding April and July. Gestation is about 39 days, with an average of one offspring per litter and a maximum of four. Young are born quite helpless, with closed eyes and weigh less than 50 g, although their hair is short, the characteristic coat pattern is already evident. Around one week of age, offspring open their eyes and by two weeks, they are able to eat meat successfully, although offspring are not completely weaned until about three and a half weeks of age. Greater grisons are fully grown at four months of age, around the same time that the testes descend in males. (Cabrera and Yepes, 1960; Dalquest and Roberts, 1951; Eisenberg, 1989; Kaufmann and Kaufmann, 1965; Leopold, 1972; Sunquist, et al., 1989)

Female greater grisons nurse their offspring until they are weaned at approximately 3.5 weeks of age. Small groups of grisons observed hunting and exploring together are usually assumed to be mothers with older offspring, indicating that offspring likely associate with their mothers for a certain amount of time post-weaning. (Dalquest and Roberts, 1951; Sunquist, et al., 1989)

Lifespan/Longevity

The lifespan of Galictis vittata has not been recorded for wild populations; although, there has been a published description of a captive grison still living at ten years and six months of age. (Yensen and Tarifa, 2003a)

Behavior

Greater grisons are primarily terrestrial and move quickly in a zig-zag pattern to various locations. While on the move through tall grass, they often pause and extend their neck and head above the grass to sniff and observe their surroundings. They have been observed burrowing and are adept swimmers; they have also been observed climbing partway up trees, apparently for exploratory purposes. Both wild and captive grisons have been described as being both playful and very inquisitive. Play often takes the form of wrestling and gentle biting. No social grooming has been observed. When faced with an unfamiliar object, grisons will slink toward the object; body outstretched, low to the ground and retract swiftly if disturbed. When alarmed, greater grisons jump backwards, snort and emit a foul-smelling musk from their anal glands, the trajectory of which, they are able to aim and use against specific targets, similar to skunks. Greater grisons tend to urinate and defecate in dark corners or nooks, generally using the same location each time. They squat and raise their tails during the act of elimination. Whether greater grisons are nocturnal or diurnal is an issue of contention among researchers. Many report that the animals are entirely diurnal, while others report that they are active throughout the night. Most, if not all, researchers appear to be in agreement that grisons are crepuscular, with periods of rest four or five hours long during the middle of the day and bouts of activity in the early morning and late afternoon. Grisons tend to sleep in burrows, such as those made by agoutis or armadillos. (Arita, et al., 1990; Bisbal E., 1986; Bisbal, 1993; Dalquest and Roberts, 1951; Eisenberg, 1989; Kaufmann and Kaufmann, 1965; Leopold, 1972; Sunquist, et al., 1989; Timm, et al., 1989)

Home Range

Wild grisons that are active during the night have been recorded traveling distances of 1.3 to 2.7 km; their individual home range has been estimated at upwards of 415 hectares, though there is a low population density within that range. (Arita, et al., 1990; Sunquist, et al., 1989)

Communication and Perception

Greater grisons communicate a number of ways, though based on observations in the field; it would seem that they have a greater reliance on olfaction than on vision. They engage in scent marking, by brushing their musk-coated tails over surfaces. Grisons also have a wide variety of vocalizations, including: snorting when alarmed or upset, purring when stroked, panting when moving from place to place, squealing during play and barking during aggressive displays. (Dalquest and Roberts, 1951; Kaufmann and Kaufmann, 1965; Kays, 1996; Sunquist, et al., 1989)

Economic Importance for Humans: Negative

Greater grisons are not valuable as game, but they may become an agricultural nuisance. In some instances they may prey on domestic chickens. (Husson, 1978; Leopold, 1972)

Conservation Status

The International Union for Conservation of Nature and Natural Resources lists Galictis vittata as a species of least concern for conservation, due to the absence of major threats and its wide area of distribution. Population trends are listed as stable. (Cuaron, et al., 2012)

Contributors

Glossary

living in the southern part of the New World. In other words, Central and South America.

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

female parental care

parental care is carried out by females

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

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This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.